Airway-related vagal preganglionic neurons express brain-derived neurotrophic factor and TrkB receptors: Implications for neuronal plasticity

Recent evidence indicates that brain-derived neurotrophic factor (BDNF) is present in neurons and may affect neurotransmitter release, cell excitability, and synaptic plasticity via activation of tyrosine kinase B (TrkB) receptors. However, whether airway-related vagal preganglionic neurons (AVPNs) produce BDNF and contain TrkB receptors is not known. Hence, in ferrets, we examined BDNF and TrkB receptor expression in identified AVPNs using in situ hybridization and immunohistochemistry. BDNF protein levels were measured within the rostral nucleus ambiguus (rNA) region by ELISA. We observed that the subpopulation of AVPNs, identified by neuroanatomical tract tracing, within the rNA region express BDNF mRNA, BDNF protein, as well as TrkB receptor. In addition, brain tissue from the rNA region contained measurable amounts of BDNF that were comparable to the hippocampal region of the brain. These data indicate, for the first time, that the BDNF-TrkB system is expressed by AVPNs and may play a significant role in regulating cholinergic outflow to the airways.